An orthophoto image widely utilized for creation of a topographic map or as a photographic map is generated by applying an orthogonal projection transformation processing to a central perspective projection image obtained by capturing a target region from the air. Recently, the image capturing equipment tends to be shifted from the conventional analog camera to a digital camera for the purpose of, for example, improving operating efficiency. For example, a UCD (UltraCamD) from VEXCEL in Austria substitutes for the conventional analog aerial camera as an analog camera for use in capturing from an airplane.
The UCD is classified into a so-called area sensor which records a predetermined area at a time as with the conventional analog aerial camera. The UCD is mounted with a plurality of CCDs and lenses in order to obtain a resolution and a capturing range equivalent to the analog aerial camera by means of an imaging device with an insufficient performance. A region to be captured is divisionally-captured as a plurality of panchromatic images, utilizing the CCDs and the lenses, whereby a wide range region is captured, and a ground resolution as the panchromatic image is improved. In the conversion of the captured image into a color image, a color image with a lower resolution is obtained by a plurality of CCDs and lenses different from the above ones, and a so-called pan-sharpening processing for synthesizing with the panchromatic image is performed, whereby the color captured image can be obtained.
Patent Document 1 describes a similar technique. In this prior art example, a wall surface is merely captured, and the image capturing equipment is not mounted in a moving platform such as an aerial camera, the image capturing distance is not extremely large, and versatile coordinate information such as a ground coordinate system is not obtained. The entire wall painting is captured as an index image, and, at the same time, the wall painting is captured to be divided into divisional detailed images. The detailed images are standardized utilizing the corresponding points of the index image, and they are connected with each other with reference to the index image. The brightness and color tone of the connected image are adjusted with reference to the index image.
Patent Document 1: Japanese Patent Application Laid-Open No. 2000-182059